What Would You Use If....

a client said "not the sugary thick cake frosting that you get when you buy a grocery store made cake" when describing what she wanted for frosting. I have only used regular shortening/butter buttercream before. I also plan on covering it with MMF so it's not going to be going on thick. But i can't remember the last time i had a store bought cake so i'm not really sure how that compares to home made buttercream. Any ideas?? thanks